Bearing supports having an annular oil damper for absorbing periodic radial movement have long been used in high speed rotating shaft applications, such as in the main bearings of a modern gas turbine engine. The annular oil damper is typically combined with a resilient mechanical centering means such as a plurality of centering rods, for supporting and positioning the bearing within the annular oil damper.
Examples of such structures are well disclosed in U.S. Pat. No. 4,429,923 issued Feb. 7, 1984 to White et al and U.S. Pat. No. 4,453,783 issued June 12, 1984 to Davis et al. The Davis and White patents show two configurations for resiliently supporting the outer bearing race within an annular oil film damper for providing the proper support to a high speed rotating shaft which is at least occasionally subject to a rotary imbalance or other radial displacement producing influences.
Another feature, disclosed in the drawings of the Davis and White references and necessary in turbomachine applications, is a shaft seal for preventing blowby of the working fluid through the bearing compartment. This sealing function is accomplished by the cooperation of a radially extending sealing surface disposed about the shaft and rotatable therewith and a non-rotating sealing ring axially adjacent the sealing surface and urged axially thereagainst for forming the desired seal.
The prior art bearing support arrangements function well in damping, supporting, and sealing the bearing structure. Modern gas turbine engine designers, however, in an effort to further increase engine efficiency and reliability, have sought to reduce the radial height of the bearing support structure in order to minimize the radius of the engine intermediate case which forms the radially inner flow barrier for the engine axial compressor section. Such a low profile bearing support structure would reduce the ratio of the hub and blade tip radii, thus both reducing engine outer diameter for a given gas flow area and increasing core engine angular velocity for a given blade tip circumferential speed.
What is needed is a bearing support structure which provides the necessary supporting, damping, and sealing functions in a low radial profile configuration.